Demonstations calling for more teachers, an end to classroom overcrowding and reform of the curriculum are spreading across the country.

From northern Lille, where protestors smashed shop windows and doors, to south west Bordeaux, where pupils released balloons to highlight their demands, the protest appears to be gaining momentum.

"We need reforms urgently," said Alice Martin of the independent students' association FIDL. "We have had nothing but promises that have never been kept."

More than half of the 2.3m students attending France's state-run senior schools are in classes of more than 30 pupils, 29% of them in classes of more than 34 pupils.

Outbreaks of violence have occurred during the protests

"We are not sardines," read a banner in western Brittany. "Father Christmas, bring us chairs and tables please," said another.

The pupils are also demanding more space in the timetable for sport and extra-curricular activities.

"The real problem is the school work-load. We want 25 hours of class and 10 hours of culture or other activities," said Martin.

"We know our problems can't be resolved in a day, but these protests are a real cry from our hearts."

In Bordeaux, 15,000 left school to demonstrate, while in nearby Toulouse police reported a similar number in the streets.

Some 10,000 young protestors caused traffic jams in Lyon, while 7,000 students turned out in Rennes, 5,000 in Grenoble, 4,000 in Pau, and 4,000 in Lille.

The wave of protest has been building up for a month following the beginning of the school year, with pupils complaining that they returned to school to find overcrowded classrooms, a shortage of teachers and poor conditions.

"May 68 - October 98" say banners appearing across France, a reference to the May 1968 student demonstrations that brought thousands of workers out on a sympathy strike against President Charles de Gaulle.

Student leaders are calling for a day of action on Thursday, with a rally in Paris to force the Socialist-led government to act.

France's Education Minister, Claude Allegre, has promised to hire new teachers but is also warning that he will be unable to meet all of the students' demands at once.